developer/Samples/NET Standard/ParallelExtensionsExtras_Standard/Extensions/EAP/SmtpClientExtensions.cs

   1 //--------------------------------------------------------------------------
   2 //
   3 //  Copyright (c) Microsoft Corporation.  All rights reserved.
   4 //
   5 //  File: SmtpClientExtensions.cs
   6 //
   7 //--------------------------------------------------------------------------
   8
   9 using System.Net.Mail;
  10 using System.Threading.Tasks;
  11
  12 namespace System.Net.NetworkInformation
  13 {
  14     /// <summary>Extension methods for working with SmtpClient asynchronously.</summary>
  15     public static class SmtpClientExtensions
  16     {
  17         /// <summary>Sends an e-mail message asynchronously.</summary>
  18         /// <param name="smtpClient">The client.</param>
  19         /// <param name="message">A MailMessage that contains the message to send.</param>
  20         /// <param name="userToken">A user-defined object stored in the resulting Task.</param>
  21         /// <returns>A Task that represents the asynchronous send.</returns>
  22         public static Task SendTask(this SmtpClient smtpClient, MailMessage message, object userToken)
  23         {
  24             return SendTaskCore(smtpClient, userToken, tcs => smtpClient.SendAsync(message, tcs));
  25         }
  26
  27         /// <summary>Sends an e-mail message asynchronously.</summary>
  28         /// <param name="smtpClient">The client.</param>
  29         /// <param name="message">A MailMessage that contains the message to send.</param>
  30         /// <param name="from">A String that contains the address information of the message sender.</param>
  31         /// <param name="recipients">A String that contains the address that the message is sent to.</param>
  32         /// <param name="subject">A String that contains the subject line for the message.</param>
  33         /// <param name="body">A String that contains the message body.</param>
  34         /// <param name="userToken">A user-defined object stored in the resulting Task.</param>
  35         /// <returns>A Task that represents the asynchronous send.</returns>
  36         public static Task SendTask(this SmtpClient smtpClient, string from, string recipients, string subject, string body, object userToken)
  37         {
  38             return SendTaskCore(smtpClient, userToken, tcs => smtpClient.SendAsync(from, recipients, subject, body, tcs));
  39         }
  40
  41         /// <summary>The core implementation of SendTask.</summary>
  42         /// <param name="smtpClient">The client.</param>
  43         /// <param name="userToken">The user-supplied state.</param>
  44         /// <param name="sendAsync">
  45         /// A delegate that initiates the asynchronous send.
  46         /// The provided TaskCompletionSource must be passed as the user-supplied state to the actual SmtpClient.SendAsync method.
  47         /// </param>
  48         /// <returns></returns>
  49         private static Task SendTaskCore(SmtpClient smtpClient, object userToken, Action<TaskCompletionSource<object>> sendAsync)
  50         {
  51             // Validate we're being used with a real smtpClient.  The rest of the arg validation
  52             // will happen in the call to sendAsync.
  53             if (smtpClient == null) throw new ArgumentNullException("smtpClient");
  54
  55             // Create a TaskCompletionSource to represent the operation
  56              var tcs = new TaskCompletionSource<object>(userToken);
  57
  58             // Register a handler that will transfer completion results to the TCS Task
  59             SendCompletedEventHandler handler = null;
  60             handler = (sender, e) => EAPCommon.HandleCompletion(tcs, e, () => null, () => smtpClient.SendCompleted -= handler);
  61             smtpClient.SendCompleted += handler;
  62
  63             // Try to start the async operation.  If starting it fails (due to parameter validation)
  64             // unregister the handler before allowing the exception to propagate.
  65             try
  66             {
  67                 sendAsync(tcs);
  68             }
  69             catch(Exception exc)
  70             {
  71                 smtpClient.SendCompleted -= handler;
  72                 tcs.TrySetException(exc);
  73             }
  74
  75             // Return the task to represent the asynchronous operation
  76             return tcs.Task;
  77         }
  78     }
  79 }